Screen vehicle comprising diphenyl, unmodified hydrogenated rosin, and its glycol esters



United States Patent SCREEN VEHICLE COIVIPRISING DIPHENYL, UN-

MODIFIED HYDROGENATED ROSIN, AND ITS GLYCOL ESTERS William C. Morris,Mayfield Heights, Ohio, assignor to The Harshaw Chemical Company,Cleveland, Ohio, a corporation of Ohio No Drawing. Original applicationOctober 21, 1950, Serial No. 191,481, now Patent No. 2,617,740, datedNovember 11, 1952. Divided and this application N ovember 3, 1951,Serial No. 254,791

2 Claims. (Cl. 260-27) This invention relates to an improved method ofapplying glass enamel or ceramic coatings to glass or metal objects, andto improved compositions for use in such process.

It has long been customary to apply designs to objects to be decoratedby the use of a screen having certain portions blocked off to form adesign. The screen process has taken numerous specific forms and, forthe most part, the enamel constituents have been suspended in a suitableoil known as screen oil. The mixture of screen oil and enamelconstituents is pressed or squeegeed through the screen into contactwith the object to be decorated, and is dried thereon. Another form ofthe screen process involves the use of a vehicle, in place of the screenoil, which is solid at the temperature of the object to be decorated,ordinarily room temperature, and which is applied at a temperature atwhich it has a suitable consistency. This form of the screen process hasthe advantage that it is not necessary to wait for the object to drybefore is is sent to the next operation. It is with this type of screenprocess that the present invention is concerned.

I have now discovered certain novel compositions of the type indicatedwhich are characterized in having highly desirable properties renderingthem suitable for the indicated use. These are useful especially in aprocess comprising applying such compositions by means of a metal screenof usual type except that it is heated during application of the designby passing electric current therethrough to an extent to keep thesurface at a temperature sufliciently above the melting point of saidcompositions to prevent clogging. In this way the compositions which areplastic or pasty at the temperature at which they are held just prior toapplication, need not be held at as high a temperature as would benecessary if the screen were not heated.

One class of compositions suitable for my purpose comprises a mixture ofpolyethylene glycols of molecular weights predominantly in the rangefrom 1500 to 6000. Minor proportions outside this range can betolerated. A very desirable combination is as follows:

Parts by weight Polyethylene glycol of molecular weight 1,540 5 to 35Polyethylene glycol of molecular weight 4,000-- to 70 Polyethyleneglycol of molecular weight 6,000 10 to 70 An optimum specific example isas follows:

Per cent Polyethylene glycol of molecular weight 1,540 20 Polyethyleneglycol of molecular weight 4,000 40 I Polyethylene glycol of molecularweight 6,000 40 "ice tion, and obliteration of screen marks in the earlyportion of the firing cycle. The polyethylene glycol material of highermolecular weight is employed for the purpose of rendering the filmrelatively hard at room temperature and toreduce the tendency of thecoating to run on firing.

The foregoing compositions can be improved by the addition of a smallpercentage of urea, although, its addition is not absolutely essential.Urea, however, is desirably added up to 7V2% of the combined weight ofpoly ethylene glycols. The urea renders the film somewhat tougher at thetemperatures at which I prefer to operate without tending to cause thecomposition to adhere to the heated screen.

The above indicated compositions may be mixed with the enamelconstituents (pigment and flux) in a ratio of from 20 to 40 parts of thevehicle to to 60 parts of the enamel constituents.

Another class of compositions may consist of (1) diphenyl, (2)hydrogenated rosin, and (3) an ethylene glycol ester of hydrogenatedrosin. Such compositions may be used in proportions, for example, asfollows:

Parts by weight Diphenyl 40 to Hydrogenated rosin of melting point 168F.,

acid value 162, and density at 25 C. 1.045 2 to 20 Ethylene glycol esterof hydrogenated rosin of melting'point 131 F., acid value 0 to 15,

and density at 25 C. about 1.06 10 to 30 To the foregoing composition itmay be desirable to add a diethylene glycol ester of hydrogenated rosinof lower melting point, for example, one having a melting point of 104F., acid value 0 to 15, and density at 25 f C. about I 1.05. This may beadded to the extent of up to 30%. It is also desirable, but notnecessary, to add a polybutene of molecular weight from 40,000 to120,000 to the extent of up to 10% of the weight of the three firstnamed constituents.

In this case, as before, the vehicle may be mixed with the refractoryenamel constituents, in the ratio of from- 20% to 40% of the vehicle to80% to 60% of the refractory components.

Diphenyl may be regarded as the fundamental vehicle, and the othermaterials as additives for modifying the properties of the diphenyl.Ethylene glycol esters, or diethylene glycol esters, of hydrogenatedrosin render the freezing point of the mixture somewhat less sharp, andmake the coating less brittle. Polybutene acts as a bodying agent andalso aids suspension of pigment in the vehicle.

Specific examples of compositions suitable for my purpose are asfollows:

Example [[1 Parts by weight Diphenyl 65 Hydrogenated rosin, meltingpoint 168 F., acid value 162, specific gravity 25 C. 1.045

Ethylene glycol ester of hydrogenated rosin, melting point 131 F., acidvalue 15, specific gravity 25 C. 1.06 25 Example IV Parts by weightComposition of Example III 100 Diethylene glycol ester of hydrogenatedrosin, melting point 104 F., acid value 15, specific gravity 25Polybutene molecular weight 40,000 5 Compositions of the-typesindicatecl'may be applied to glass or metal in the following manner:

The composition made up of the above indicated vehicle, together withthe enamel constituents in the proportions indicated, is applied to theglass or metal surface through a screen having a suitabledesign. Thetemperature of the composition just before application will be such asto afford the desired working consistency and preferably will be fromabout 55 C. to 115 C. The screen will be heated by the passage of anelectric current therethrough, and will be maintained at a temperatureat or somewhat above the temperature of the composition to be applied tothe screen, preferably about 5 C. thereabove or about 60 C. to 120 C.The objects to be decorated will ordinarily be at room temperature(usually 25 C. to 35 C.) although they may be somewhat above or somewhatbelow room temperature. In any event, the temperature of the object tobe decorated will be sufficiently below the freezing temperature of thecomposition to be applied that immediately upon application thecomposition will freeze, thus permitting another application of adifferent color'immediately. in the case of multicolor printing, orpermitting immediate transfer of the objects to the lehr where theorganic material is driven off by the calcination leaving the inorganicenamel constituents fused on the objects to be decorated.

Screen enamels of various types may be used. The low melting fluxes ofthe lead bore-silicate type mixed with suitable coloring oxides andvarious additions for imparting specific properties to the enamels, suchas TiOz for acid resistence, are typical. The above describedcompositions not only have properties suitable for the application, butvolatilize on firing without causing defects in the enamel coating.

It will be understood that the components of the composition arethoroughly admixed before being applied. The mixing is best accomplishedby grinding the ingredients together suitably in a paint mill of thethree-roll type. Desirably the vehicle, the enamel ingredients, and themill, are all maintained at a temperature within the range from 100 C.to 110 C. during the mixing, each being preheated to that temperaturerange before the mixing operation is commenced.

This application is a division of my co-pending application Serial No.191,481, filed October 21, 1950, now Patent No. 2,617,740, issuedNovember 11, 1952.

Having thus described my invention, what I claim is:

1. A composition suitable for use as a vehicle for the application ofenamel by a screen process, the same comprising diphenyl to the extentof 40 to 90 parts by weight; a hydrogenated rosin of melting point about168 F., acid value about 162, and density at 25 C. about 1.045,-to'

the extent of from 2 to parts by weight; an ethylene glycol ester ofhydrogenated rosin of melting point about 131 F., acid value about 15,and density at C. about 1.06, to the extent of from 10 to parts byweight; a

diethylene glycol ester of hydrogenated rosin of melting:

point about 104 F., acid value about 15, and density-at 25 C. about1.05, up to 30 parts by weight; and polybutene, molecular weight from40,000 to 120,000, up to 10 parts by weight.

2. A composition suitable for application by the screen processcomprising 2 to parts of the composition defined in claim 1, and 80 toparts of enamel pigments and enamel flux combined.

References Cited in the file of this patent UNITED STATES PATENTS2,331,803 Schla-anstine Oct. 12, 1943 2,462,037 Davis et al Feb. 15,1949 2,462,631 Gittings 'et a1 Feb. 22, 1949 I 2,505,740 Mavis et alApr. 25, 1950 2,532,699 De Coste Dec.'5, 1950

1. A COMPOSITION SUITABLE FOR USE AS A VEHICLE FOR THE APPLICATION OFENAMEL BY A SCREEN PROCESS, THE SAME COMPRISING DIPHENYL TO THE EXTENTOF 40 TO 90 PARTS BY WEIGHT; A HYDROGENATED ROSIN OF MELTING POINT ABOUT168* F., ACID VALUE ABOUT 162, AND DENSITY AT 25* C. ABOUT 1.045, TO THEEXTENT OF FROM 2 TO 20 PARTS BY WEIGHT; AN ETHYLENE GLYCOL ESTER OFHYDROGENATED ROSIN OF MELTING POINT ABOUT 131* F., ACID VALUE ABOUT 15,AND DENSITY AT 25* F., ACID 1.06, TO THE EXTENT OF FROM 10 TO 30 PARTSBY WEIGHT; A DIETHYLENE GLYCOL ESTER OF HYDROGENATED ROSIN OF MELTINGPOINT ABOUT 104* F., ACID VALUE ABOUT 15, AND DENSITY 25* C. ABOUT 1.05,UP TO 30 PARTS BY WEIGHT; AND POLYBUTENE, MOLECULAR WEIGHT FROM 40,000TO 120,000, UP TO 10 PARTS BY WEIGHT.